least one gunman took 13 people hostage on Monday at a chocolate shop in
Sydney, Australia
, local TV news was
 reporting live
. Police had closed off a number of streets in the area and had evacuated nearby office buildings, authorities said.

State and federal police were responding to the incident, the prime minister said, and police have urged people to leave or avoid the area.

"Police are dealing with an armed incident and specialist officers are attempting to make contact those inside a café,"
New South Wales
police said in a statement.

The Lindt chocolate shop is in
Martin Place
, a busy tourist, transportation and shopping district that is home to several major banks, including the Reserve Bank of
. At one point, a black flag resembling the
standard was shown in the shop's window.

Those people still in buildings on streets bordering
Martin Place
were warned to "remain indoors and away from open windows," police said.

New South Wales
police said on social media that some streets in the area were closed and some suburban rail services were suspended.
's Channel 7 News, which reported that there were 13 hostages, said the nearby Sydney Opera House had been evacuated.

Prime Minister Tony Abbott said he had spoken with the
New South Wales
leader, Mike Baird, and offered him support and assistance. The National Security Committee has also met for briefings on the hostage situation, he said in a statement.

"This is obviously a deeply concerning incident but all Australians should be reassured that our law enforcement and security agencies are well trained and equipped and are responding in a thorough and professional manner," he said.

The U.S. Consulate in
Americans to stay away from the area.

The hostage incident comes after police performed a series of major anti-terrorism raids throughout
in September, The Sydney Morning Herald
reported. Following those operations, police alleged that Islamic extremists were planning to behead a person in
Martin Place

"This looks all too like our worst fear being realized," Greg Barton, a Middle East and terrorism expert at
, told Channel 7 News.

The black flag was being misreported as an
flag, said Barton, who described it as a more general Islamic standard that "has been used by jihadi groups as a battle banner." Its use "suggests almost certainly that we're looking at some sort of terrorist attack," he said.

"Up until now, there has not been this wave of attacks [in
], but that appears to be what's happening here," Barton said.

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